Chapter 6 - Nervous System Flashcards
Erasistratus
Father of physiology
William harvey
Demonstrated heart pumps through a system of closed vessels
Walter Cannon
Coined term homeostasis, ‘wisdom of the body’
August Krough
Krough principle - animals can be used to study human problems, comparative studies
Peripheral Nervous System - sections
Autonomic and somatic
Autonomic Nervous system
Part of PNS
Controls involuntary movement - smooth and cardiac muscle,glands, and GI neurons
Sympathetic and parasympathetic
Two neuron chain b/w CNS and effector organ
Excitatory or inhibitory
Sympathetic
PNS - autonomic
Fight or flight
Parasympathetic
PNS - autonomic
Rest and digest
Somatic NS
Voluntary muscle movement except reflex arcs
Single neuron b/w CNS and skeletal muscle cells
Innervates skeletal muscle
Leads only to muscle excitation
Reflex arc steps
Stimulus - receptor - integrating center - effector - response
Central Nervous system
Brain and spinal cord
Cell body
Contains nucleus and ribosomes
Receives and gathers all input from other neurons
Dendrites
Receives input increases surface area
Info in form of NT
Undergo graded potential
Axon
Carries output to a target cell
AP travel to axon terminal can release NT
Myelin
Covers axon Highly modified plasma membrane Made of proteins Increases speed of AP Produced in oligodendrocytes and Schwann cells Insulator - less ion leakage Reduces metabolic costs (energy used)
Nodes of ranvier
Gaps b/w myelin where axon plasma membrane is exposed to extracellular fluid
Decreases number of potential changes which adds to speed
Axon Motor proteins
Kinesin- anterograde
Dynein - retrograde
Connected to micro tumbles
Anterograde transport
Kinesin protein
Cell body to axon terminal
Mvmt of nutrients, NT, enzymes, mitochondria
NT housed in secretory vesicles
Retrograde transport
Dynein protein
Axon terminal to cell body
Mvmt of recycled membrane vesicles, growth factors
Afferent neurons / sensory neurons
Carries info from tissues and organs (sensory receptors) to CNS
Efferent neurons / motor neurons
Carries info from CNS out to effector cells
Interneurons
Connect neurons w/in the CNS
Most abundant
Nerve
Group of many nerve fibers traveling together in PNS
Nerve fiber
Axon of a neuron
Synapse
Junction b/w two neurons where electrical activity in one neuron influences excitability of second
Glial Cells
Oligodendrocytes Astrocytes Microglia Ependymal cells Schwann cells
Oligodendrocytes
Form myelin on axons in CNS
Astrocytes
Regulate composition of ECF in CNS
Remove K+ ions and NT around synapses
Help form BBB
Provide glucose to neurons
Microglia
Specialized macrophages that perform immune functions in CNS
Ependymal cells
Formation of cerebral spinal fluid
Line fluid filled cavities of brain and spinal cord
Makes up choroid plexus in third ventricle
Schwann cells
Produces myelin in PNS
Resting Membrane Potential
-70 mV
Established by Na+/K+ pump
Inside: K+, slightly negative
Outside: Na+, slightly positive
Sodium potassium pump
Creates and maintains electrical potential
3 Na out
2 K in
Uses up to 40% cell ATP
Leaky Channels
Only moves one type of ion
Maintains correct potential difference
Polarize
Outside of the cell have a different charge (RMP)
Depolarized
Potential becomes less negative / closer to 0
Overshoot
Reverse of membrane potential
Inside become positive
Repolarize
Membrane potential that has been depolarized
Hyperpolarize
Potential is more negative than RMP
Graded potential
Occurs in all cells
Confined to a really small region of membrane
Magnitude of potential change varies with stimulus strength
Decay overtime
Can be excitatory or inhibitory
Action potential
Large alterations in memb. Potential -70 to +30 mV (larger than graded)
Always returns to RMP
Rapid: 1-4 sec.
Only in excitable membranes: muscle and nervous
Sodium Voltage gated channels
Fast to respond to changes in memb.
Have inactivation gate (ball and chain)
Potassium voltage gated channels
Slower - causing hyperpolerization
No inactivation gate leading to slowness
Absolute refractory period
Membrane cannot produce another AP because Na+ channels are inactivated
Relative refractory period
VG K+ channels are open making it harder to depolarize to threshold
2nd AP can occur but only if stimulus is strong enough
How AP travels
Travels down axon if membrane is depolarized to threshold potential
Opening of Na+ channels
Can’t move backwards because membrane is in a refractory period
Saltatory conduction
To leap
Synapse
Anatomically specialized action b/w two neurons
100 trillion synapses in CNS
Convergence
Many neurons communicate with one secondary neuron
Divergence
One primary neuron communicates with many secondary neurons
Electrical synapse
Plasma membrane of pre and post synaptic cells are joined by gap junctions
Continuing propagation of AP
EX cardiac and smooth muscle
Chemical synapses
Chemical message in the form of NT is passed from the pre-synaptic neuron through the synaptic cleft to the post-synaptic neuron
Two kinds of postsynaptic potential
Excitatory (EPSP) - depolarization, graded potential, + entering
Inhibitory (IPSP) - hyperpolarization, graded potentials at beginning stages, -ve charged ion going in
Presynaptic proteins
Synaptotagmin
SNAREs
Synaptotagmin
Binding site for Ca
SNAREs
Keeps NT vesicles loosely attached to presynaptic memb.
Postsynaptic receptors
Ionotropic
Metabotropic
Ionotropic receptor
Ion channel postsynaptic receptors
Metabotropic receptors
Act indirectly as postsynaptic ion channels through G proteins pro 2nd msgr. Channel
Temporal summation
Two or more membrane potentials produced at different times are added together
Potential change is greater than that caused by single input
Spatial summation
Two or more inputs occurring at the same time in different locations on the neuron are added together
Potential change greater than that caused by single input
Axo-axonic synapse
Presynaptic synapse where an axon stimulates the presynaptic terminal of another axon
Presynaptic inhibition
Inhibitory input to neurons through synapses at the nerve terminal
Presynaptic facilitation
Excitatory input to neurons through the synapses at the nerve terminal
Autoreceptors
Receptor on a cell affected by a chemical messenger released from the same cell
Receptor desensitization
Temporary inability of a receptor to respond to its ligand due to prior ligand binding
Types of neurotransmitters
Acetylcholine
Biogenic amines
Amino Acids
Neuropeptides
Acetylcholine (ACh)
Major NT in PNS at neuromuscular junction
Cholinergic neurons
Neurons that release ACh
Acetylcholinesterase
Enzyme that degrades excess ACh
Two types of ACh receptors
Nicotinic
Muscarinic
Nicotinic receptor
Responds to ACh and nicotine
Ion channel for both Na and K
Muscarinic Receptor
Responds to ACh and muscarine
Metabolic receptor coupled with g protein
Parts of the brain
Forebrain: cerebrum and diencephalon
Cerebellum
Brain stem
Cerebral hemispheres
Parietal, occipital, temporal, frontal
Gray matter
Outermost
Mostly cell bodies
White matter
Innermost
Mostly myelinated fibers
Gyri
Raised ridges of cerebral cortex
Sulcus
Intentions of cerebral cortex
Thalamus
In forebrain - diencephalon
Plays a role in arousal and focused attention
Hypothalamus
In forebrain - diencephalon
Master communication center / integration center
Important for neuronal ad endocrine coordination
Pituitary gland
Important endocrine structure
Limbic system functions
Thalamus and hypothalamus: Learning Emotions Appetite Sex Endocrine integration
Cerebellum
Important for controlling movements and posture and balance
Parts of the Brainstem
Midbrain
Pons
Medulla oblongata
fn of brain stem
Relay center b/w forebrain, cerebellum, and spinal cord
Blood Brain Barrier
Semipermeable membrane barrier that separates circulating blood from brain extracellular fluid in the CNS
Meninges of BBB
Pia mater - inner (next to brain)
Arachnoid mater - middle, web like
Dura mater - outermost
Subarachnoid space
B/w pia mater and arachnoid mater
Filled with cerebral spinal fluid
CSF travels there from lateral ventricle were it is produced
